The invention relates to the field of internal combustion rotary engines, and more specifically, to such engines of the oscillatory rotating type.
Engines as sources of mechanical force play a vital part in modern civilization. The most common type of engine today is an internal combustion engine based on a reciprocating piston arrangement and crank drive. The disadvantages of reciprocating engines are numerous and well known. They are heavy, of complex construction, use many moving parts, subject to relatively rapid wear, and utilize fuel at a very poor rate of efficiency. Also their emissions represent the largest constituent of urban atmospheric pollution worldwide. Today, more than ever before, all industries utilizing combustion engines are faced with restrictions as to the amount of pollutants exhausted by the engine. The engine-related noise and vibrations are also seen as significant health hazards that are long due for improvement.
Due to imminent fossil fuel shortages the industry is pressured to provide engines that are more fuel efficient. The consumers and user industries alike expect engines to become progressively lighter, smaller, more durable and reliable while at the same time they should also become simpler and cheaper to manufacture, operate and maintain.
The reciprocating engine has been with us for over a hundred years and during that time the design effort has been tremendous producing a multitude of improvements in all aspects of engine operation and performance. By now the reciprocating engine design has been developed to a near-perfect state with further improvement becoming ever more difficult and costly to achieve. Current efforts mainly center around the use of latest materials and fabrication techniques, sophisticated control systems and increasingly complex sub-systems such as variable electronic valve trains or direct fuel injection. While the continuing massive investments in related R & D keep producing diminishing returns in the form of ever costlier solutions the result is still short of the growing consumer expectations and in many cases the gap is widening. The obvious conclusion is that a break-through can only be achieved by a radical departure from the conventional reciprocating piston engine design.
For decades corporations and individual inventors all over the world have been coming up with designs of engines that would go a long way towards meeting the emerging requirements by achieving a more direct energy conversion without the use of a reciprocating piston. The type of arrangement that has shown the most promise is the so-called "rotary engine". A rotary engine is known as utilizing a rotor which is enclosed in a chamber and rotated by an expanding ignited gas to convert heat energy into mechanical energy in order to perform work. Some of the advantages thus achieved are as follows: higher volumetric output and power density due to multiple utilization of work space during one revolution; higher uniformity of torque due to multiple work strokes during one revolution; higher cumulative efficiency due to more effective phasing and lower loss to friction; simpler construction due to absence of a forced phasing mechanism and reduced vibration and noise due to lower numbers of poorly balanced parts.
The different arrangement, shape and motion of the rotor classify rotary engines into different types, the best known of which are at present the eccentric rotor type, movable vane type and oscillatory rotating engine.
The best known of the three is the eccentric rotor engine, more commonly known as "the Wankel engine". It is the only one to have achieved a limited commercial success. First built by a German engineer in mid-1950s it was at one time described as "revolutionary" and attracted a lot of development effort and funds. A number of automotive companies invested considerable resources in bringing Wankel-based products to market but all such projects bar one Mazda have since been aborted. Numerous patent applications have been filed and patents issued for this engine type e.g. U.S. Pat. No. 2,988,065 issued to Wankel et al. on Jun. 13, 1961, U.S. Pat. No. 3,174,466 issued to Scherenberg on Mar. 23, 1965, U.S. Pat. No. 3,483,849 issued to Yamamoto on Dec. 16, 1969, U.S. Pat. No. 3,667,311 issued to Louzecky on Jun. 03, 1975, U.S. Pat No. 4,308,002 issued to DiStefano on Dec. 29, 1981 and U.S. Pat. No. 5,203,307 issued to Burtis on Apr. 20, 1993.
The Wankel engine employs a generally triangular eccentrically rotating piston disposed within an elongate, generally oval chamber. The piston rotates within the chamber and alternatingly intakes a fuel mixture, compresses it, ignites it, and exhausts it, the same cycle as a reciprocating engine but with rotary motion. Mechanically this engine was a substantial simplification over the conventional reciprocating piston-type internal combustion engine because it greatly simplified phasing and because linearly reciprocating pistons, interconnected by complicated crankshafts, have been eliminated. However, the Wankel engine has caused serious concerns regarding pollution as in this type of engine, due to its inherent falcate shape of the chamber, poor combustion conditions prevail. Another effect of the poor combustion conditions is a high level of fuel consumption. Further, due to the complex shapes employed the Wankel engine is complex to manufacture and repair. Its seals are another problem area: even the most successful and known Wankel engine uses around twenty individually spring loaded sealing members working in a hard-to-machine epitrochoidal cavity where they are subjected to extreme wear and tear. Not surprisingly the engine's life span is generally somewhat limited.
Another variety of rotary engines is the so-called "sliding vane" type. In this type of arrangement use is made of a plurality of vanes mounted inside the rotor. The vanes slide in and out of the rotor to create separate energy chambers inside the engine. This type of engine is disclosed in a number of patents such as U.S. Pat. No. 4,401,070 issued to McCann on Aug. 30, 1983, U.S. Pat. No. 5,727,517 issued to Mallen on Mar. 17, 1998, U.S. Pat. No. 5,758,617 issued to Saito on Jun. 02, 1998 and U.S. Pat. No. 5,937,820 issue to Nagata on Aug. 17, 1999. This type of rotary engine has attracted some commercial interest e.g. the Rotary Engine being developed by Reg Technologies in Canada but the general design has inherent problems that are similar to those experienced in connection with the Wankel engine: sealing of the vane tips and wear-and-tear to which the rotor-mounted segments of the vanes are subjected. The design gets more and more complex as attempts are made to eliminate or alleviate these problems, such design complexities hardly conductive to reduced cost or extended life span of the engine.
An oscillatory rotating engine employs a plural number of rotors with interleaved vanes around the center of rotating. By changing the angular velocity of the rotors an oscillatory movement is superimposed on their uniform rotation, thus modifying the volume of the energy chambers defined by each pair of adjacent vanes and the inner surface of the engine housing. An inlet port, exhaust port and ignition device are provided at appropriate points on the housing, so that the expansion and contraction of the working chambers will provide induction, compression, expansion and exhaust strokes. The forces that alternately drive adjacent pistons apart or together are transformed through a motion transforming mechanism into forces that drive the output shaft.
The oscillatory rotating engines disclosed to date fall into two broad categories depending on the shape of the housing: cylindrical or toroidal. The toroidal arrangement presents greater manufacturing problems, requires more complex phasing and makes less efficient use of the space it occupies.
Regardless of the housing shape, oscillatory engines include a number of types depending on the drive mechanisms used to control the oscillatory motion of the rotors. The principle types of mechanism used for controlling this motion include ratchet stops, camming arrangements, elliptical gear arrangements or crank and planet gear arrangements.
Thus a type of ratchet mechanism is first disclosed in U.S. Pat. No. 1,003,80 issued to Rodigin in 1911 and in a number of more recent patents e.g. U.S. Pat. No. 4,279,577 issued to Appleton Jul. 21, 1981, U.S. Pat. No. 5,400,754 issued to Blanco Palacios et al. Mar. 28, 1995.
A variety of camming arrangements, first introduced by Tschudi in 1927, is more recently disclosed in a number of patents e.g. U.S. Pat. No. 4,035,111 issued to Cronnen in July 1977, U.S. Pat. No. 4,390,327 issued to Picavet on Jun. 23, 1983, U.S. Pat. No. 5,484,272 issued to Horn on Jan. 16, 1996.
A number of inventors have devoted their efforts to creating a drive mechanism for the oscillatory rotating engine based on the use of elliptical gears. Some of them are Way U.S. Pat. No. 3,112,062 of 1960, Sabet U.S. Pat. No. 3,203,405 of 1965, Groger U.S. Pat. No. 3,430,573 of 1966, Boes U.S. Pat. No. 3,873,247, Minka U.S. Pat. No. 4,010,716 of 1977, Seybold U.S. Pat. No. 4,057,374 of 1977, Sakita U.S. Pat. No. 5,133,317 of 1992 and Lopez U.S. Pat. No. 5,844,708 of 1998.
The main objection with the prior art drive/phasing mechanism designs as outlined above is that they employ arrangements that lack inherent robustness. In explosive engines of the rotary type it is the universal experience that it is difficult or impossible to so construct and arrange ratchets, cams or elliptical gears as to enable them to withstand the excessive shocks to which they are subjected by the sudden impulses imparted to the mechanism by the explosive character of the motive power. The shock loads in all of these arrangements are limiting their operation to slower speeds and shorter life and therefore they have not gained any wide acceptance.
The type of oscillatory rotating engine employing a drive mechanism based on the use of cranks and planet gears, is frequently referred to as the Kauertz engine after the inventor of one of its early embodiments; see U.S. Pat. No 3,144,007 of 1960. More recent examples of prior art include U.S. Pat. No. 3,937,187 issued to Bergen on Feb. 10, 1976, U.S. Pat. No. 4,068,985 issued to Baer on Jan 17, 1978, U.S. Pat. No. 4,072,447 issued to Gaspar on Feb. 07, 1978 and a number of U.S. patents issued to Wintry U.S. Pat. No. 5,433,179 on Jul. 18, 1995, U.S. Pat. No. 5,622,149 on Apr. 22, 1997, U.S. Pat. No. 5,686,269 on Nov. 11, 1997.
This type of drive is inherently more robust as it is based on the use of the crank technology that has been well proven and perfected over the decades of piston engine development. Wider acceptance and significant commercial use of this arrangement has however been prevented by a number of problems unresolved in prior art.
Despite its inherently more robust nature, this arrangement is also subject to heavy loadings of the drive mechanism packed into a limited space along with large variations of loads, a condition which is compounded by the limited space available on the single side of the engine housing where the mechanism has traditionally been located. Such loads have a particularly negative effect where they impact the meshed teeth of the planet pinions and single sun gear, e.g. as shown in Wittry U.S. Pat. Nos. 5,433,179, and 5,622,149. This leads to excessive strength requirements imposed on individual drive components, resultant output power constraints and difficulties in achieving mass production. The above drawbacks become particularly critical in trying to implement the Diesel cycle with its associated higher efficiency but much higher peak pressures and corresponding forces impacting the drive mechanism. Most prior art oscillatory engines are open to objections of this type.